The known industrial application of high-temperature superconductors (type-II superconductors) is at present still quite restricted. In these superconductors, magnetic fields create vortices that allow superconducting current to travel around these formed vortices up until a certain critical point. Eventually, as the magnetic field strengthens, or as the critical current or temperature is exceeded, the vortices begin to move about and interfere with the material's superconductivity, introducing resistance. One way to immobilize vortices and recover zero resistance at high magnetic fields is vortex pinning. However, decades of research have, to the best of knowledge, failed to yield strong vortex pinning over a wide range of applied magnetic fields.
For over sixty years, it has been understood that the ground state vortex structure is a hexagonal lattice. Subsequently, methods have been developed in an attempt to increase the critical current using uniform pinning arrays (i.e. holes or indentations) that incorporate periodicity to match the vortex structure. In these methods, pinning is enhanced at commensurate fields when the number of vortices equals an integer multiple of the number of pinning sites, but away from these specific matching fields, the enhancement of the critical current is lost.
Therefore, it would be advantageous to develop a vortex pinning arrangement that potentially exhibits a stronger vortex pinning effect over a much larger range of magnetic field than found in traditional periodic and/or random pinning arrangements.